Speaker 1: 0:00

All right, I got a case for you. It's a 34-year-old that comes in and they're complaining that they've got diplopia. And you see them and they're sitting up at the edge of the bed and their head's kind of floppy. And you start talking to them and they're kind of mumblish and you're not exactly sure what's going on. You do a quick neurological exam and everything seems fine. There's no sensory findings, but they clearly have some bulbar muscle weakness and difficulty swallowing. So you ask yourself what could this be? And there's no signs of infection. There's no signs of IV drug use, no history of IV drug use. And we talked about botulism in the past. But this is a mimica that can look a lot like botulism and it turns out as you get further history that this person has a history of myasthenia gravis.

Speaker 1: 0:52

Myasthenia gravis, let's talk about it. Let us discuss this disorder very quickly. So myasthenia gravis is an autoimmune disease. It's an autoimmune disease of the motor end plant. So if we look down here, you've got your axons, you got your motor end plate and then you get these antibodies To those motor end plates and they don't work so well. So when the acetylcholine releases and it goes to the motor end plate, it doesn't depolarize that well because there's not that many of those little places for it to get in. So it is a problem with not release of acetylcholine but the motor end plates. There's not enough targets for the acetylcholine to do its thing. So it's an autoimmune disease affecting the pneumosteal adjuction. It's got antibodies to the acetylcholine receptors and it's classically and this is important it classically has a fluctuating course Good some days, bad the others. Good in the morning, bad in the afternoon, vice versa. And that's important because a lot of the other disorders, like Guillain-Barre, like botulism, tend to get worse and worse and worse, and this is one of those ones that has a fluctuating course. So the key features are oh, get back there. The key features are those ocular findings, the bulbar findings, so ocular findings where they've got diplopia, but it's actually classically pupillary, sparing, and then the dysarthria, the dysphonia, the difficulty chewing, and you know they'll start with chewing some chewing gum and then after five or 10 minutes they're like I can't do it anymore. So that's sort of a classic thing thing.

Speaker 1: 2:25

The respiratory symptoms is what we really care about. So they have dyspnea, they have respiratory muscle weakness, they can have difficulty swallowing, which is a problem for their airway, of course, and then they have generalized weakness. They can't climb stairs and climb, you know, combing their hair and stuff can be a problem. So so the myasthenic crisis, this is the key thing. So this is myasthenia plus respiratory compromise. Myasthenic crisis is myasthenia plus respiratory compromise, and that respiratory compromise can be that they just can't breathe because they've got so much muscle weakness in their diaphragm. But it can also be because they can't swallow, they've got airway problems, they've got airway obstruction, they've got aspiration pneumonia, for example. So anything that basically affects their ability to breathe we're going to call a myasthenic crisis, and this can be triggered by a whole bunch of things Surgery, pregnancy, infection, lots of activity, stress in general. The medications there's a whole bunch, but the classic things is aminoglycosides and fluoroquinolones and beta blockers my handwriting is absolutely and there's just a whole bunch. Don't even try and remember them all. Just know that before you give a myasthenic patient any drug, you better check that it's not going to make things worse. So diagnosis and treatment If you suspect this and it's not a prior diagnosis, the classic thing now is this ice pack test, which is where you put an ice pack over their eyeballs and you look at their eyeballs beforehand and see if they can open their eyelids all the way up.

Speaker 1: 3:58

And they usually can't because they're in a bit of a crisis. That's why they're seeing you and they've got ptosis, so their eyes are hanging down. So you put ice bags over their eyeballs and then after about five minutes or so you take it off and if it's significantly better, that's a really good indication that you've got myasthenia. There's a lot of different mechanisms why people think that works about nerve conduction, about increased amount of acetylcholine that's in that synaptic cliff because it's getting metabolized less. A whole bunch of reasons I don't think you need to know about. But that's the test we do now. We used to do this thing called the Tensilon test, but it's gone away. It was kind of dangerous and didn't work well anyway.

Speaker 1: 4:32

And then obviously the other bedside test is you want to do that single breath count so we've done this for other disorders which affects those bulbar muscles, the respiratory muscles, and so that's again when you take a breath all the way in and then you start to count out about two numbers per second one, two, three, four, five. If they can't get to 20, that is a real problem. But you also need to do another sort of full assessment of how are they coughing, how they handling their secretions. But if that single breath count doesn't get to 20, if it's less than 20, then you've got to think about I need to stick a tube or something in this patient We'll talk about that in a second and then definitive testing is not going to occur in the emergency department. Basically it's about antibody testing and then you can do all those EMG and other studies, but that's not what you're going to be doing in the emergency medicine department or in the urgent care.

Speaker 1: 5:18

And then the key management principles for these patients is that if they're sick, if they're not breathing very well, then help them, do BiPAP, do CPAP, give them oxygen while you work out what to do and maybe call a friend hey, help me out with this one. If you decided that you actually have to put a tube in, you have to breathe for this person. Here is the key thing Try and do it without paralytics. Often they are so weak at that point that you can just give them an induction agent ketamine weak at that point that you can just give them an induction agent, ketamine atomidate, and you can slip the tube in If you have to use a paralytic, then you have to reduce the amount of rocuronium, or you have to increase the dose of succinylcholine.

Speaker 1: 5:54

Remember, when you give succs, then you're releasing acetylcholine to sort of overwhelm those receptors and then you depolarize all the muscles, but there's not enough receptors, so you have to use more of it to depolarize them. That's the way I think about it. And then with rocuronium it's the exact opposite. So you might have to use two milligrams per kilogram of the sucks and instead you might have to do 0.5 milligrams per kilogram of rock. All right, that's a really important thing to remember. So please remember that. Do nothing or increase the sucks or decrease the rock.

Speaker 1: 6:28

We talked about respiratory sport. We talked about non-invasive ventilation. And then the medications. You can give them steroids in these acute settings, but about 50% of the time the steroids can make them worse. So talk to a consultant about that. Definitively, what's going to happen upstairs once you admit them to the ICU is they're going to get IVIG or plasma exchange, but that takes days to a week or more to work and you can give Pfizer stigmine, but usually when they're in crisis that makes things worse. So, again, the Pfizer stigmine can be used as an ongoing treatment for these patients, but in a crisis situation it can actually make things worse. So you have to be very careful about this one. Just get ready with your airway stuff because it might get worse.

Speaker 1: 7:15

So let's go back. And the key feature to this thing is bulbar muscle weakness. It fluctuates, it often has pupillary sparing. It's not caused by an ascending paralysis. It's not progressive over time. It tends to fluctuate and come and go and you've got loss of those motor implants because it's an autoimmune disease. And the key thing is try and avoid intubation if you can, but if you have to tube these patients, remember decrease the rock. But if you have to tube these patients, remember decrease the rock, increase the sucks. Quick overview myasthenia gravis, herbert outzies, invictus Reviews.